Microalgae cultures within a growing vessel comprise a number of undesirable contaminant or foreign substances besides the primary algae type intended to be grown and harvested. These undesirable substances may comprise pollutants, growth inhibitors, predators, competitors, detritus, dirt and other suspended or settled solids, and clumped algae. The growth inhibitors may comprise, but are not limited to, algae metabolites, cell debris, bacteria, coliform bacteria, fungi, detrital matter, dissolved organic matter, fecal matter, and other micro-particles. The competitors and predators may comprise an invasive algae type other than the primary algae type of the culture, and zooplankton that feed on phytoplankton.
The growth of algae in terrestrial systems such as open ponds or bioreactors may be improved by removing contaminants from the algae culture. Removal of contaminants from the algae culture may enhance the growth rate and health of the algae culture due to a decrease in competition for nutrients, gases, and light, and a decrease in substances that are directly and/or indirectly harmful, toxic, or poisonous to the primary algae type.